Autocapture pacing/sensing configuration

Abstract

A cardiac electrical stimulation system that enhances the ability of the system to automatically detect whether an electrical stimulus results in heart capture or contraction. The cardiac electrical stimulation system may be utilized, for example, as a cardiac pacer or as a cardioverter defibrillator. The cardiac electrical stimulation system includes an electrical stimulation circuit that attenuates polarization voltages or “afterpotential” which develop at the heart tissue/electrode interface following the delivery of a stimulus to the heart tissue, which thereby allows the stimulation electrodes to be utilized to sense an evoked response to the electrical stimulus. The cardiac electrical stimulation system utilizes the stimulation electrodes to sense an evoked response, thereby eliminating the necessity for an indifferent electrode to sense an evoked response. The present invention allows accurate detection of an evoked response of the heart, to thereby determine whether each electrical stimulus results in capture.

1. A method for operating a cardiac rhythm management device, comprising:
 switchably connecting at least two electrodes disposed in an atrium or a ventricle to the inputs of a sense amplifier; 
 delivering an electrical stimulus to the atrium or ventricle through a coupling capacitance wherein the electrical stimulus is delivered between at least one of the electrodes connected to the sense amplifier and a housing of the device; 
 attenuating afterpotentials resulting from the delivered electrical stimulus by reducing the coupling capacitance; and, 
 sensing an evoked response to the electrical stimulus from the output of the sense amplifier. 
 
     
     
       2. The method of  claim 1  wherein the coupling capacitance is reduced by switchably connecting a capacitor to an electrode connected to the sense amplifier. 
     
     
       3. The method of  claim 1  wherein the coupling capacitance is reduced by switchably connecting a first coupling capacitor in series with a second coupling capacitor. 
     
     
       4. The method of  claim 1  wherein the electrical stimulus is delivered between an atrial tip electrode and a housing of the device. 
     
     
       5. The method of  claim 1  wherein the electrical stimulus is delivered between a ventricular tip electrode and a housing of the device. 
     
     
       6. The method of  claim 1  wherein the evoked response is sensed between an atrial ring electrode and a ventricular electrode. 
     
     
       7. The method of  claim 1  wherein the evoked response is sensed between two ventricular electrodes. 
     
     
       8. The method of  claim 1  wherein the evoked response is sensed between an atrial ring electrode and a ventricular ring electrode. 
     
     
       9. The method of  claim 1  wherein the evoked response is sensed between an atrial ring electrode and a housing electrode. 
     
     
       10. The method of  claim 1  wherein the evoked response is sensed between an atrial ring electrode and a ventricular coil electrode. 
     
     
       11. The method of  claim 1  wherein the evoked response is sensed between an atrial ring electrode and a superior vena cava coil electrode. 
     
     
       12. The method of  claim 1  wherein the evoked response is sensed between an atrial tip electrode and a ventricular coil electrode. 
     
     
       13. The method of  claim 1  wherein the evoked response is sensed between an atrial tip electrode and a ventricular tip electrode. 
     
     
       14. The method of  claim 1  wherein the evoked response is sensed between an atrial tip electrode and an atrial ring electrode. 
     
     
       15. The method of  claim 1  wherein the evoked response is sensed between a superior vena cava coil electrode and an atrial tip electrode. 
     
     
       16. The method of  claim 1  wherein the evoked response is sensed between a superior vena cava coil electrode and a ventricular coil electrode. 
     
     
       17. The method of  claim 1  wherein the evoked response is sensed between a superior vena cava coil electrode and a ventricular tip electrode. 
     
     
       18. The method of  claim 1  wherein the evoked response is sensed between a ventricular tip electrode and a ventricular coil electrode. 
     
     
       19. The method of  claim 1  wherein the evoked response is sensed between a superior vena cava coil electrode and a ventricular ring electrode. 
     
     
       20. The method of  claim 1  wherein the evoked response is sensed between a ventricular ring electrode and a ventricular coil electrode.